The mission of Childrens Hospital Los Angeles (CHLA) is "to advance the health and well-being of children and adolescents by integrating medical care, preventive services, medical education, and research in response to the needs of our community and in an atmosphere of love, compassion, and respect for people." Since the early 1980's, the Division of Adolescent Medicine at CHLA has focused on reducing risks for young people through innovative models of service, research and training established in partnership with the community. Through these programs, the Division provides health care, mental health, case management, health education, and substance abuse treatment services to over 9000 youth annually, and is involved in community-level interventions for pregnancy, HIV, and violence prevention. Since the inception of the Adolescent Trials Network (ATM), CHLA has established itself as a productive Adolescent Medicine Trials Unit (ATU), contributing to the primary mission of the ATUs in the recruitment and retention of subjects in clinical trials and production of high quality data. In the area of behavioral trials, CHLA has far greater participation and recruitment than any other ATM site. For community prevention trials (Connect to Protect[unreadable]), CHLA is one of the first three (of fifteen) sites to complete the index interviews and begin the brief venue based surveys. As for therapeutic trials, CHLA has consistently been in the top third for recruitment. The quality of our site management is reflected in consistently positive reviews at our semi-annual site visits. The Los Angeles ATU has not only established itself as a productive ATU, but has contributed to the ATM through active involvement in committees and the development of new behavioral protocols. The site PI has been the ATU chair for all five years of this project and served on the Executive and Site performance committees. In addition, CHLA is one of the few ATU sites to have initiated an ATN protocol (ATN 039). CHLA is currently in the process of developing yet another original protocol involving the use of cell phones as reminders to address non-adherence. The following application documents that Childrens Hospital Los Angeles (CHLA), Division of Adolescent Medicine has the experience, expertise and infrastructure necessary to participate as a site in the ATN. Our core staffing plans will allow us to continue effective recruitment and retention into therapeutic, behavioral and community trials. In addition our experienced staff will continue to be active in the development of new protocols and thus allow us to continue to contribute to the ATN scientific agenda. The ATN research agenda is of particular relevance to public health, as it will significantly contribute to our understanding of HIV in adolescents.